PM2002DP Ver la hoja de datos (PDF) - South African Micro Electronic Systems
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PM2002DP Datasheet PDF : 10 Pages
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PM2002DP
CTTERMINATIONRESISTOR
Provisionismadefortheuseofacurrenttransformeronthe
module. The existing shunt needs to be removed and the
current sense resistors will have to be recalculated for the
specificcurrenttransformer.ThevoltagedropacrosstheCT
terminationresistoratratedcurrentshouldbeatleast20mV.
The C T ' s u s e d s h o u l d h a v e a l o w p h a s e s h i f t a n d a r a t i o o f
1:2500.The CT is terminated with a 2.7Ω resistor giving a
voltagedropof864mVacrosstheterminationresistoratrated
conditions
CURRENTSENSORINPUTRESISTORSFIGURE5(USING
ACURRENTTRANSFORMER)
TheresistorsR6,R7definethecurrentlevelintothecurrent
senseinputsthedevice.Theresistorvaluesare selectedforan
inputcurrentof16µAonthecurrentinputsatratedconditions.
For an 80A-ratedmetertheresistorvaluesarecalculatedas
follows:
R 6 = R 7 = ( IL/ 1 6 µ A ) x RSH / 2
=80A/16µAx2.7Ω / 2
=2.7kΩ
IL= Linecurrent
RSH=CTTerminationresistor
2500=CTratio
L J5
LIVEIN
CT1 IIN
R6
R16
LIVEOUT
IIP
R7
Figure5:Currentinputconfiguration
PhaseCompensation(Whenusingacurrenttransformer)
Phase shift caused by the current transformer may be
correctedbyinsertingacapacitorinthevoltagedividercircuit.
SeeFigure6,CapacitorC7.Tocompensateforaphaseshiftof
0.18degreesthecapacitorvalueiscalculatedasfollows:
C=1/(2x π xMainsfrequencyxR5xtan(Phaseshiftangle))
C=1/(2x π x50x1Mxtan(0.18degrees))
C=1.013µF
ReferenceVoltageVREF
TheVREFpinoftheSA2002Disconnectedtoaresistorthat
determinestheonchipbiascurrent.
GroundGND
The G N D p i n o f t h e S A 2 0 0 2 D i s t o t h e l i v e p h a s e , w h i c h i s
halfway between VDD and VSS. Note that supply bypass
capacitorsC1andC2arepositionedascloseaspossibletothe
supply pinsofthedevice,andconnected to a solid ground
plane.
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